The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
An engine combusts a mixture of air and fuel, producing drive torque. Engines such as diesel engines and compression ignition engines produce particulate matter (PM) that is filtered from exhaust gas by a particulate filter. The filter reduces PM by collecting and storing PM. Over time, the amount of PM stored in the filter may increase. A full filter may decrease exhaust flow relative to a clean filter.
During regeneration, the filter may be cleaned by burning PM within the filter. Regeneration may involve heating the filter to a combustion temperature to ignite PM. Combustion of PM further increases the filter temperature. The rate of regeneration of the filter and the filter temperature may be affected by an oxygen level in the exhaust. Increased oxygen levels in the exhaust may increase the rate of regeneration and the filter temperature.
There are various ways to perform regeneration, including modifying engine control, using a fuel burner, using a catalytic oxidizer, using microwave energy, and/or using resistive heating coils. The resistive heating coils may be arranged in contact with the filter to allow heating by both conduction and convection.
Engines may produce ash that accumulates near an outlet of the filter. Combustion of ash requires higher temperatures than combustion of PM. The higher temperatures (e.g., near 1400° C.) required to combust ash may damage the filter. Thus, regeneration may be conducted at lower temperatures that combust PM but do not combust ash. As a result, an amount of ash stored in the filter may increase over time. As the amount of ash stored in the filter increases, a volume available within the filter to regenerate PM decreases.